1. Field of the Invention
The present invention relates generally to a hydraulic pump apparatus, and more particularly to an engaging member for preventing a sleeve mounted in a housing of the hydraulic pump apparatus from rotating with respect to the housing.
2. Related Art
There is known a conventional hydraulic pump apparatus of a plunger type for supplying a brake fluid of the brake apparatus for a vehicle, for example. FIG. 1 is a sectional view showing the conventional hydraulic pump apparatus 1.
The conventional hydraulic pump apparatus 1 is provided with a sleeve 2, a plunger 3 slidably mounted in the sleeve 2, an eccentric cam 4 having a cam shaft 5, a motor 6 engaging with the cam shaft 5. The sleeve 2 is fluid-sealingly accommodated in a housing 7, and the motor 6 is mounted in the housing 7.
A suction passage 8 is formed in the housing 7 and communicated with a reservoir 9, for example. The fluid ejected from the hydraulic pump 1 is supplied to a master cylinder 11 through an ejection passage 10 formed in the housing. In the sleeve 2, a fluid introducing passage 12 is provided for communicating the suction passage 8 with a plunger chamber 14 formed in the sleeve 2 through the suction valve 13, and a communicating passage 15 is provided, which communicates with the plunger chamber 14 through an ejection valve 16 and an ejection port 17. The communicating passage 15 also communicates with the ejection passage 10 through a passage 19 of a set plug 18.
The suction valve 13 is composed of a ball 20 and a valve spring 22 for urging the ball 20 against a valve seat 21 of the sleeve 2. On the other hand, the ejection valve 16 is composed of a ball 23 and a valve spring 26 accommodated in a spring holder 25 for urging the ball 23 against a valve seat 24 of the sleeve 2.
When the plunger 3 which always contacts to the eccentric cam 4 by an elastic force of the spring 27 slides in a direction by which a capacity of the plunger chamber 14 increases, the ball 20 removes from the valve seat 21 to thereby introducing the fluid from the reservoir 9 into the plunger chamber 14 through the suction passage 8 and fluid introducing passage 12. On the other hand, the plunger slides in a direction by which the capacity of the plunger chamber 14 decreases, the fluid contained in the plunger chamber 14 is pressurized so that the ball 23 removes from the valve seat 24 to thereby eject the fluid in the chamber 14 to the master cylinder 11 through the communicating passage 15, fluid passage 19 and ejection passage 10.
The sleeve 2 is tightly fitted in a cylindrical hole 28 formed in the housing 7, and a boss part 30 of the sleeve 2 is pushed by a plug screw 29 so that the sleeve 2 is urged toward a hole end part 31. The boss part 30 of the sleeve 2 is provided with a pin hole 32 and the housing 7 is provided with a pin hole 33. A solid rotation-preventing pin 34 is fitted in the pin hole 32 of the boss part 30 and the pin hole 32 of the housing 7, so that the sleeve 2 is prevented from rotating in the housing.
As described above, the conventional hydraulic pump apparatus employs the solid rotation-preventing pin 34 for preventing the sleeve 2 from rotating, it is necessary to provide the pin hole 32 in the boss part 30 of the sleeve 2 and the pin hole 33 in the housing 7. For such a structure, the boss part 30 must be large enough to accommodate the pin hole 32. That is, the length of the boss part 30 must be elongated by an amount of a diameter of the pin hole 32 and, accordingly, the length of the housing 7 is elongated. As a result, the hydraulic pump apparatus 1 will disadvantageously be large in size and heavy in weight. The hydraulic pump apparatus for use in a vehicle such as an automobile is required small in size and light in weight.